In recent years, in order to improve environmental performance such as fuel consumption of automobiles, automobiles such as electric automobiles, hybrid automobiles, and fuel cell powered automobiles, which utilize electric power as well as conventional internal combustion engines, have been rapidly developed and put on the market. Each of these automobiles is equipped with a power conversion equipment for converting electricity to power. Further, in order to cope with higher output and highly efficient packaging, a water cooling system using engine coolant liquid is the mainstream in cooling heat-generating elements in the power conversion equipment. Along with the water cooling, a housing of the power conversion equipment, which is mounted in an engine room, is required to be vibration proof, waterproof, salt-water proof, and dust proof.
Meanwhile, in order to cope with functional improvement, the housing of the power conversion equipment houses components such as: a water cooling heat sink for cooling heat-generating elements such as switching elements; a control circuit board; a step-up converter; etc. Further, the housing of the power conversion equipment houses components such as: a smoothing capacitor for suppressing ripple current; a terminal block for power supply connection; a terminal block for motor connection; etc. These components are electrically connected by use of high-voltage and low-voltage harnesses and bus bars.
As for the power conversion equipment equipped with many components as described above, in order to realize size/weight reduction, cost reduction, improved vibration proof property, and improved assembly performance, a structure as follows has been proposed. That is, each of components such as a control circuit board is housed in a housing that also serves as a structure material, and housings in which the respective components are housed are fastened to each other. Thereafter, electrical connection is executed by use of service holes of the housings, and finally, the service holes are closed with rubber plugs. Further, each rubber plug has a disc-shaped flange, and the rubber plug is inserted until the flange comes into contact with the housing during assembly, which provides excellent assembly performance (for example, refer to Patent Document 1).
Furthermore, in order to improve sealing performance, a structure has been proposed in which a cylindrical cup-shaped cored bar having a flange projecting inward of the housing is provided inside the rubber plug, to increase and uniformize the surface pressure of a resin that comes into contact with a housing-side cylindrical seal surface, and moreover, a lip seal is provided on a disc-shaped flange (for example, refer to Patent Document 2).